Deciphering indigenous bacteria in compacted bentonite through a novel and efficient DNA extraction method: Insights into biogeochemical processes within the Deep Geological Disposal of nuclear waste concept

Compacted bentonites are one of the best sealing and backfilling clays considered for use in Deep Geological Repositories of radioactive wastes. However, an in-depth understanding of their behavior after placement in the repository is required, including if the activity of indigenous microorganisms...

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Veröffentlicht in:Journal of hazardous materials 2021-04, Vol.408, p.124600-124600, Article 124600
Hauptverfasser: Povedano-Priego, Cristina, Jroundi, Fadwa, Lopez-Fernandez, Margarita, Shrestha, Rojina, Spanek, Roman, Martín-Sánchez, Inés, Villar, María Victoria, Ševců, Alena, Dopson, Mark, Merroun, Mohamed L.
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Sprache:eng
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Zusammenfassung:Compacted bentonites are one of the best sealing and backfilling clays considered for use in Deep Geological Repositories of radioactive wastes. However, an in-depth understanding of their behavior after placement in the repository is required, including if the activity of indigenous microorganisms affects safety conditions. Here we provide an optimized phenol:chloroform based protocol that facilitates higher DNA-yields when other methods failed. To demonstrate the efficiency of this method, DNA was extracted from acetate-treated bentonites compacted at 1.5 and 1.7 g/cm3 densities after 24 months anoxic incubation. Among the 16S rRNA gene sequences identified, those most similar to taxa mediating biogeochemical sulfur cycling included sulfur oxidizing (e.g., Thiobacillus, and Sulfurimonas) and sulfate reducing (e.g., Desulfuromonas and Desulfosporosinus) bacteria. In addition, iron-cycling populations included iron oxidizing (e.g., Thiobacillus and Rhodobacter) plus reducing taxa (e.g., Geobacillus). Genera described for their capacity to utilize acetate as a carbon source were also detected such as Delftia and Stenotrophomonas. Lastly, microscopic analyses revealed pores and cracks that could host nanobacteria or spores. This study highlights the potential role of microbial driven biogeochemical processes in compacted bentonites and the effect of high compaction on microbial diversity in Deep Geological Repositories. [Display omitted] •Optimization of an effective DNA extraction method from highly compacted bentonites.•Pores and cracks in compacted bentonite were showed by microscopic analyses.•High bacterial diversity was identified in specimens up to 1.7 g/cm3 of dry density.•Bacteria mediating the S and Fe biogeochemical cycles were enriched by acetate.•No significant differences on microbial diversity were marked after 2-years period.
ISSN:0304-3894
1873-3336
1873-3336
DOI:10.1016/j.jhazmat.2020.124600